Sow longevity impacts start before they are born

Gilts born as part of small litters are much more likely to develop into productive sows

Sows have become much more productive since Flowers started his career 32 years ago. They are better able to produce large litters consistently and able to produce enough milk to raise those piglets. Photo:
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Dr. Billy Flowers.photo: John Greig

Sows are leaving farms long before they reach the stage of profitability, says Dr. Billy Flowers, one of North America’s best-known sow reproduction experts.

Flowers, a professor at North Carolina State University, says the situation isn’t conducive to long-term productivity for the pork sector.

His research shows that farmers may need to select gilts based on factors determined before they are born.

Why it matters: Sows that are productive longer are more profitable as the most money is made after the costs of raising them are paid. Sow longevity is also a potential animal welfare issue.

“This is not a sustainable system for our sow farms in the U.S. or anywhere else,” said Flowers at the recent London Swine Conference.

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Swine Management Services, which provides data management for almost a quarter of all pigs raised in the United States says the culling rate for sows in the U.S. is 47 per cent per year. That’s well below the three parities, or pregnancies, that are needed before a sow becomes profitable.

Flowers said most of the culling can be attributed to reproductive issues.

Hog farmers can take steps to improve their culling rate, and research by Flowers shows that there are issues even earlier than most would expect that influence sow survival and reproductive efficiency.

Birthweight and the size of litter the gilt is from have a significant impact on success as sows.

Farms producing sows for genetics need to better understand the impact of birthweight and be cautious about litter size, Flowers said.

Gilts tend to get more attention when being readied for delivery to the barn where they will be grown into sows ready for first parity. Sows also get attention when the decision is made to breed them for the first time.

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Less attention is paid to the early developmental phase, which starts after conception.

Gilts that grow in larger litters have less room to grow and therefore have less development of their organs at birth. Animals with less developed brain, livers and intestines will have more challenges at birth, said Flowers.

Sows have become much more productive since Flowers started his career 32 years ago. They are better able to produce large litters consistently and able to produce enough milk to raise those piglets. Most of that progress has been made by genetic selection.

It may be time to put greater selection pressure on factors affecting sow longevity, but they can be opposite to the needs of commercial farms.

In a study, Flowers weighed pigs at birth and weaning and set up the litters so that there were only seven piglets nursing per sow, so the only variable was the difference in litter size during lactation.

Gilts were managed exactly the same during the rest of their growth periods and were sent to two commercial sow farms. About 40 per cent of the gilts from smaller litters were still in the herd after second parity, compared to 12 per cent from larger litters.

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He also looked at birthweight and longevity. Gilts born at less than 1.1 kgs had almost no chance of being in the herd long term, compared to gilts born at 1.6 kg birthweight.

Flowers said that using selection criteria for sow longevity at the multiplication stage can help, but he understands that not every system will want to apply selection criteria at multiplication.

An alternative is to focus on getting gilts off to a good start by ensuring colostrum intake and encouraging preweaning growth.